The mechanism of tolerance induction in model systems in vivo and in vitro will be studied using fluoresceinated antigens and hapten-specific purification to isolate specific cells which bind antigen. The cell surface and molecular changes in these cells will be analyzed including the role of IgD and IgM. The discrimination of different B & T lymphocyte subpopulations will be emphasized. The importance of surface Ig isotypes and mitogen receptors in priming and tolerance induction will be studied. In addition, lymphocyte clones will be established, using somatic cell hybridization of isolated hapten-specific lymphoid cells. Manipulation of various immune responses will be attempted using carrier T cell tolerance as well as B cell tolerance to T-dependent and T-independent antigens.